1. Field of the Invention
The present invention relates to a high frequency device for controlling a high frequency signal used, e.g., for satellite communications, ground microwave communications, or mobile communications, etc.
2. Background Art
Japanese Laid-Open Patent Publication No. H08-288701 discloses a microwave integrated circuit device provided with feed-though portions. The feed-through portions of this microwave integrated circuit device have a characteristic impedance of 50Ω.
High frequency devices with a power amplifier for use in the transmitter section of a base station are sometimes designed to have a discrete configuration including only a power amplifier FET chip, or a “partial match” configuration including only an FET chip and a pre-matching substrate, in order to reduce the number of matching circuit substrates. In such a case, it is desirable that the feed-through portions of the high frequency device have the desired impedance (e.g., 50Ω). Therefore, the feed-through portions and the dimensions of the high frequency device are designed so as to achieve impedance matching to the semiconductor chip or matching circuits used.
Once the feed-through portions and the dimensions of the high frequency device have been designed and a prototype of the high frequency device has been made, it is not easy to change the impedance of the feed-through portions. This means that if the configuration of the semiconductor chip or the matching circuits is later changed, it is difficult to achieve optimum matching conditions, resulting in degraded performance of the high frequency device.